Continuous flow mixing apparatus of the internal recirculating type



May 17, 1966 J P BOLANOWSKI ETA!- CONTINUOUS FLOW MIXING APPARATUS OF THE INTERNAL REC IRCULATI NG TYPE 3 Sheets-Sheet 1 Filed Feb. 24. 1965 INVENTORS JOHN P. BOLANOW$K\ GEORGE W. REIGEL BY wz. SAMO ATTORNEY May 17, 1966 J. P. BOLANOWSKI ET AL 3,251,577

CONTINUOUS FLOW MIXING APPARATUS OF THE INTERNAL RECIRCULATING TYPE Filed Feb. 24, 1965 3 Sheets-Sheet 2 INVENTORS JOHN P. BOLANOWSKI GEORGE W. REGEL BY 40,5. SAW/ML ATTORNEY May 17, 1966 J P BOLANOWSKI ETAL 3, 51,577 CONTINUOUS FLOW MIXING APPARATUS OF THE INTERNAL 6 RECIRCULATING TYPE 19 5 S Sheets-Sheet 5 Filed Feb 24,

United States 4 Patent 3,251,577 CONTINUOUS FLOW MIXING APPARATUS OF THE INTERNAL RECIRCULATING TYPE John P. Bolanowski, Jeifersonville, and George W. Reigel,

Clarksville, Ind., assignors to Chemetron Corporation,

Chicago, III., a corporation of Delaware Filed Feb. 24, 1965, Ser. No. 439,509 14 Claims. (Cl. 259-7) This is a continuation-in-part of co-pending application Serial No. 282,681, filed May 23, 1963, now forfeited.

This invention relates to an improved mixing apparatus of the internal recirculating type and more particularly to such an apparatus in which an improved control of the degree of mixing and of the quality of the mixed product may be secured. Various forms of mixers having inter-.

nal recirculation have been proposed. Some of these mixers partake of a significant pumping action as well as the mixing function and the efii'ciency of the mixing is often compromised, if not actually subordinated to the pumping action. It is a pu'r-pose'of our present invention to provide a mixing apparatus in which the function of mixing is paramount to other factors.

Apparatus of the type exemplified by this invention can be used in the homogenizing, mixing, whipping, aerating, emulsifying, dispersing or reacting of flo/wable materials and accordingly is not limited to use for any one purpose or with any one material although it is particularly well suited for hand-ling high liquid shear products.

An object of the invention is to provide an improved mixing apparatus having an inlet leading thereto and an outlet leading therefrom at the respective regions of maximum and minimum pressures within the apparatus.

Another object is to provide a simple and compact mixing apparatus capable of handling a wide variety of materials and with variable rates of flow thereof.

A (further object is to provide an improved mixing apparatus which may be readily assembled and disassembled for cleaning and other purposes.

A still further object is to provide an improved mixing apparatus of the recirculating type in which the incoming unmixed material is channeled under pressure into the recirculating material at the region of maximum pressure.-

Still a further object is to provide an improved mixing apparatus having an efficient sealing means preventing leakage from the interior of the apparatus.

In the drawings, which illustrate suitable forms of apparatus embodying the invention, I

FIG. 1 is a side elevational view of the apparatus and its driving means with the conduits for the material being omitted.

FIG. 2 is a front end elevational View of the apparatus shown in FIG. 1.

FIG. 3 is a sectional view of the mixing apparatus, with parts broken away, taken on line 3-3 of FIG. 2 and to FIG. 7 is a detail view illustrating an alternative meansfor deflecting material from the recirculating'space to the mixing space.

FIG. 8 is a vertical sectional view illustrating another alternative means for deflecting material from the recirculating space to the mixing space, and

FIG. 8A is a top plan view of one of the deflecting 3,251,577 Patented May 17, 1966 vanes, each having an inclined end carried by the rotating structure.

FIG. 9 is a sectional view of an alternative form of the mixing apparatus, with parts broken away.

FIG. 10 is a sectional view taken along line 1010 of FIG. 9.

FIG. 11 is a sectional view taken along line 1111 of FIG. 9, and FIG. 12 is a fragmentary sectional view of another alternative form of the mixing apparatus.

Referring first to FIGS. 1 and 2 the mixing apparatus of our invention comprises a unitary device indicated generally at 10 and which is driven by a suitable source of power indicated generally at 11. As will be understood, a piping system (not shown) will be detaohably connected to an inlet 12 and to an outlet 13 of the ap paratus, and that system downstream from the mixer will generally incorproate a conventional adjustable'back pres-, sure valve for use in regulating the throughput and amount of recirculation to be used with a given material under treatment. Likewise, the piping system upstream from the mixer will incorporate the necessary conventional conduits, :pumps and adjustable valves employed in furnishing to the mixer a material or materials to be treated in their proper proportions and at the proper' pressures, as illustrated, for example, in US. Patent No. 2,898,092.

'In one form, the mixer includes a generally drumshaped casing indicated at 14 and having a stationary first head member 15 spaced from a. movable second head member 15A by a circular peripheral wall 16 upon which the inlet 12 is mounted. The head member 15A mounts the outlet 13 (generally at the axis of rotation of the mixer for a purpose later to appear, and preferably is pivotally mounted upon the first head member 15 by a hinge having multiple hinge plates 17, 18, 19 permitting the second 7 head member 15A to be pivoted to one side for maintenance purposes after the piping system is disconnected and after a series of bolts 20 joining the first and second head members have been removed. Movement of the second head member 15A from'its first assembled position as shown to a second position wherein it is suspended only by the hinge gives access to the compartment within the casing 14.

The first head member 15 includes a supporting framework having a mounting plate 21 spaced from the head member 15 by rigid posts 22. This mounting plate is adapted for attachment to a companion plate 23 on the frame enclosing the reduction gearing of a conventional variable drive unit 24 and from which the driving shaft 25 of the mixer extends. In one satisfactory form of the invention, the power drive comprises a conventional variable drive unit with a range of from 1480 to 247 rpm. and which is manually adjustable by the usual crank 26 (FIG. 2) extending from one side of the motor frame 27. This motor frame inturn includes a rigid pedestal with feet 28 adapted to be bolted to a stationary surface and the motor frame supports a conventional electric motor 29 mechanically coupled to the variable drive unit 24.

Passing now to FIGS. 3, 4 and 5 there is shown an improved hollow elongated hub member 30 adapted to embrace and to be keyed to shaft 25, this hub member having a relatively thin sleeve portion 30A for extending through the first head member 15 of the casing 14 and a relatively massive hub portion 31 confronting the second head member 15A. Securely afiixed to the hub portion 31 as by welding are a plurality of impeller blades 32 uniformly spaced from each other angularly about the hub portion 31 and having a curved configuration which serves to avoid pulling of material within the recirculating space toward the hub member 30 as the hub member 30 turns. Attached to the inner edges of these blades as by welding is an annular bafile plate 33 concentrically mounted on the hub member 30 and with an inner diameter greater than that of the hub member 30 and providing an annular opening 34. The outer diameter of the baffle plate 33, however, is less than the inner diameter of the circular wall 16 of the casing 14 (FIG. 3) thus providing an annular space 35 for return of material impelled outwardly by theaction of blades 32. Rigidly aflixed to the baflle plate 33 on the side opposite the blades are a plurality of concentric arrays of mixing elements or pins 36, the distal ends of which, when the rotor is assembled within the casing, lie in close proximity to the inner face of the first head member 15. These pins are of a character to have any desired crosssectional shape and are not necessarily limited to the circular form as shown.

As seen in FIGS. 3 and 6, the head member 15 includes an axial opening 40 through a central hub portion 41, the opening 40 being adapted to receive the shaft 25 and the sleeve portion 30A, and having an end recess into which a conventional seal 42 is secured. Inboard of the seal 42 is a hollow seal insert 43 preferably of bronze or equivalent material and having an O-ring seal 44 interposed between the seal insert 43 and the inner wall of the head member 15. The seal insert 43 is backed by an annular metallic seal body 45 having another O-ring seal 46 engageable with the hub member 30. A backing ring 47 with a resilient washer 48 interposed between the backing ring 47 and the enlarged hub portion 31 serves to prevent leakage of material along'the shaft 25.

A circumferential shoulder 50 extends about the inner face of the head member 15 inboard of holes 51 which receive the bolts and a similar shoulder 52 extends about the inner face of the head member 15A, each of these shoulders bounding a shallow recess into which O-rings 53 and 54 are received for sealing between the edges of the circular wall 16 of the casing and the respective head members. ion to the first head member 15 adjacent the circular wall 16 and extending into annular return space 35 and terminating adjacent the second head member 15A, are a plurality of recirculating deflectors 55 spaced uniformly circumferentially of the first head member 15. The distal ends of these deflectors are curved to extend in an angular direction opposite the direction of rotation of the blades 32. Rigidly atfixed to the inner face of the stationary head member 15 are a plurality of concentric arrays of mixing elements or pins 56 the distal ends of which, when the hub member 30 is assembled in the casing 14, lie in close proximity to the confronting face of the baflie plate 33. These pins are similar in size and number to the mixing pins 36- on'the baffle plate 33 but are arranged on radial distances from the shaft which are different from those of the cooperating mixing pins 36 and preferably with radial differences in distance which will cause the pins 36 on the moving baffle plate 33 to move within about 0.0625 inch of the stationary pins.

The end of the shaft 25 is provided with a keyway 60 ,(FIG. 3) adapted to receive key 61 which also engages in a keyway 62 (FIG. 4) in the hub portion 31. In addition, the end of the shaft 25 is threaded to receive a threaded screw 63 attached to cap 64, and an O-ring seal 65 is interposed between that cap and the end of the shaft 25.

When fully assembled, outer edges 32A of the impeller blades 32 clear the inner face of the second head member 15A by a suitable distance.

With the foregoing description in mind, the advantages of the invention will be more clearly understood by considering the forces exerted upon material entering the apparatus through the inlet 12. With the rotor turning at a speed determined by the setting of the variable drive mechanism, material flows centripetally through the impelled contrifugally into the annular return space 35,

Aflixed in cantilever fashpassing meanwhile through the recirculating space 34A between the baffle plate 33 and the second head member 15A. Depending, however, upon pressure conditions obtaining in the system and upon the speed of the shaft 25, another portion of mixed material flows around the cap 64 and then through the outlet 13, thus giving a continuous flow through the apparatus while internal recirculation is simultaneously being accomplished.

Material caught by the blades 32, moreover, slides therealong and acquires a progressively greater peripheral velocity as it approaches the return space 35 which represents the region of greatest internal pressure within the apparatus. The pressure of this moving recirculated material opposes the pressure of incoming material being supplied through the inlet 12 and prevents short-circuiting flow between the inlet and outlet through the recirculating space. As the recirculated material reaches the return space 35 it strikes the curved deflectors 55 and is cammed or deflected into the path of additional material being supplied through the inlet 12, after which it mixes with and moves with that additional material through the primary mixing space. As a result of those flows an exceptionally thorough and efiicient mixing action is secured, and which is believed to be attributable in large part to the relative locations of the inlet and outlet. The curved shape of the impeller blades also is believed to provide eflicient impelling of the mixed material. As will be apparent, the centrifugal pumping action effected by the impeller blades is essentially for the purpose of recirculating material rather than to force mixed material from the machine. Material contained within the casing 14 is effectively prevented from leaking therefrom by the novel sealing means above described and which in combination with the other portions of the apparatus forms a significant feature of the invention. In general, these seals are capable of withstanding pressures in the order of 300 p.s.i. and the proper assembly of the same is expedited by having the second head member 15A of the casing 14 so mounted that rapid and unrestricted access to the interior of the casing 14 can be had.

The mixing apparatus of the invention also can be readily controlled to handle many varieties of material or materials in the same machines. For example, such control can be exerted solely by varying the speed of the shaft 25, by varying the setting of the downstream back pressure valve (when used), by varying the pressure upon material supplied to the inlet 12, or by any combination of these conventional controls (not shown). Of particular significance, the recycle control exerted upon any chosen material can be easily accomplished by varying the speed of the shaft 25, by varying the setting of the downstream back pressure valve, or by any combination of these conventional controls.

Various modifications of the described apparatus can be resorted to without departing from our invention. For example, any or all of the casing head members 15 and 15A and wall member 16 may incorporate heat exchange facilities.

Referring now to FIGS. 9, 10 and 11, there is shown an alternative form of mixing apparatu generally indicated at 10'. The mixing apparatus 10' includes many of the same components as the mixing apparatus 10 and thus wherever possible like reference characters are used, along with a prime symbol. The apparatus 10' has a generally drum-shaped casing 14 having a stationary first head member 15' spaced from a movable second .the impeller blades 32'.

and forms the end of the hub member 30.

head member A by circular or. annular peripheral wall 16 having an inlet 12'. The first head member 15' includes a supporting framework having a mounting plate 2.1 spaced from the head member 15 by rigid posts 22. A series of bolts join the first and second head members 15' and 15A.

Rigidly aflixed to the inner face of the stationary head member 15 are a plurality of concentric mixingelements or pins 56' the distal ends of which, when the hub member 30' is assembled inthe casing 14', lie in close proximity to the confronting face of baffle plate 33'. These pins 56 are similar in size and shape to the mixing pins 36 on the bafile plate 33' and are arranged at radial distances from shaft 25' which are different from those of the cooperating mixing pins 36' and preferably with radial differences in distance which will cause the pins 36 of the moving bafiie plate 33' to pass closely past the stationary pins.

Secured to a hub portion 31' of a hub member as by welding are a plurality of impeller blades 32' uniformly spaced from each other angularly about the hub portion 31' and having a curved configuration which serves to avoid pulling material within the recirculating space toward the hub member 30' as the hub member 30' turns. Attached to the inner edges of the impeller blades 32 as by welding is the annular baffle plate 33' concentrically mounted on the hub member 30 and with an inner diameter greater than that of the hub member 30 to provide an annular opening 34'.

A baflle plate 80 is spaced from the baffle plate 33 by The baflle plate 80 is also mounted concentrically with respect to the shaft 25' on the hub portion 31 of the hub member 30'. Screws 81 re- -movably secure the baflle plate 80 to the impeller blades 32. As the baffle plate 80 has a central aperture 82 of the same inside diameter as the outside diameter of the hub portion 31', material in a recirculating space exist ing between the baffle plates 33 and 80, and which is impelled in the outward direction relative to the hub 30', cannot pass between the baffle plate 80 and the hub portion 31'.

Curved deflectors 55' in the space 35 can deflect at least a part of the material into the space which exists between head member 15' and the baffle plate 33'. .Due-

to the difference in pressure between the inlet 12 and the outlet 13, some of the material passes through an annular passage or space 83 between the outer periphery of the batfle plate 80 and the inside of the circular wall 16 and into the space which exists between the baflle plate 80 and the head member 15A. Mixing elements or pins 84 extend from the head member 15A toward the baffle plate 80 and cooperating elements or pins 85 extend from the baffle plate 80 toward the head member 15A. The free ends of the mixing elements or pins 84 lie in close proximity to the baffle plate 80, while the free ends of the mixing elements or pins 85 lie in close proximity to the head member 15A.

A cap or plate 64' is mounted at the end of the shaft 25' The hub member 30' terminates short of, and in alignment with, the bore of the outlet 13';

Material to be mixed continuously passes under pressure through the inlet 12 into a space existing between head member 15" and baflle plate 33', where the cooperating pins 36 and 56 subject the material to intense mixing action. The mixed material continuously passes through the opening 34' in the bafl le plate 33' and into the space between the bafile plates 33' and 80. The blades 32 impel the mixed material toward the annular wall 16. Deflectors 55' direct some of the material. across the space 35 and into the space between the head member 15 and the baflle plate 33 for further mixing. The balance of the material passes through the outlet space 83 to the mixing space between the bafile plate 80 and the head member 15A, where the mixing pins 84 and 85 cause-material to be further intensely mixed. The mixed material is continuously discharged through the outlet Referring now to FIG. 12, there is shown an alternatlve form of mixing apparatus generally indicated at 10" The mixing apparatus 10 includes the same components as the mixing apparatus 10 except that there are no co-' operating mixing elements extending from the head member 15 toward the baffle plate 80 or from the baffle plate 80" toward the head member 15A. The baffie plates 33" and 80" are secured to the impeller blades 32". Mixing elements 36" extend from the baffie plate 33" toward the head member 15'. and mixing elements 56" extend from the head member 15 toward the baffle plate 33". i

As another example, the invention is in no way limited to the type of deflectors 55 and 55' as shown respectively in FIGS. 3 and 6 and in FIGS. 9 and 12. As seen in FIG. 7, the deflection of the material moving under the influence of the rotating blades 32 can be accomplished by providing deflecting projections formed by rifiing grooves 70 or the like formed integrally with the inner surface of the peripheral wall It? and terminating at their forward ends in a plane lying between the first head member 15 and the baffle 33. As a further example, the deflection of the material may be accomplished by suitable deflectors 71 at the terminal ends of. each of the blades 32 (FIGS. 8 and 8A) and carried by those blades and by the baffle 33 as they rotate as a unit. Accordingly, we do not restrict ourselves to the particular form of these or other features of the invention as illustrated, but rather intend to avail ourselves of all modifications that fall within the scope of the appended claims.

What is claimed is: I

1. In a continuous flow mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having a longitudinal axis, said casing defining a chamber, an inlet leading from a source of material under pressure into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft disposed along said axis and mounted for rotation within said chamber, a baffle plate extending transversely of said chamber and dividing said chamber into a mixing space and a recirculating space, mixing elements extending from said first head member toward said baffle plate, cooperating mixing elements extending from said baflle plate toward said first head member, a discharge opening in said baflie plate adjacent said shaft providing communication between said mixing space and said recirculating space, said baffle plate terminating short of said Wall to define a return space, means in said recirculating space for impelling at least a substantial portion of the mixed material toward said wall, said bafile plate and said impelling means being fixedly mounted for rotation with said shaft, and means for deflecting at least some of the mixed material from said recirculating space into said return space and then into said mixing space.

2. In a continuous flow mixer: a casing including a first head member and a second headmember joined by a generally annular Wall, said wall having a longitudinal axis, said casing defining a chamber, an inlet leading from a source of material under pressure through said wall into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft disposed along said axis and mounted for rotation within said chamber, a bafile plate extending transversely of said chamber and dividing said chamber into a mix ing space and a recirculating space, mixing elements extending from said first head member toward said baffle plate, cooperating mixing elements extending from said baffle plate toward said first head member, a discharge opening in said baffle plate adjacent said shaft providing communication between said mixing space and said resaid wall to define a return space, impelling blades in said recirculating space for impelling at least a substantial portion of the mixed material toward said wall, each impelling blade having an outward terminal end, the maximum pressure in said chamber being at said terminal ends of said impelling blades and at said return space, said baffle plate and said impelling means being fixedly mounted for rotation with said shaft, and means for deflecting at least some of the mixed material from said recirculating space into said return space and then into said mixing space, said inlet being located to channel at least some of the incoming material directly into the mixed material at the place of maximum pressure.

3. In a continuous fiow mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having a longitudinal axis, said casing defining a chamber, an inlet leading from a source of unmixed material under pressure through said wall, into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft disposed along said axis and mounted for rotation within said chamber, a bafile plate extending transversely of said chamber and dividing said chamber into a mixing space and recirculating space, mixing elements extending from said first head member toward said baffle plate, cooperating mixing elements extending from said bafile plate toward said first head member, a discharge opening in said baffle plate adacent said shaft providing communication between said mixing space and said recirculating space, said bafile plate terminating short of said wall to define a return space, impelling means spanning a sutficient distance between said bafile plate and said second head member for impelling at least a substantial amount of the mixed material toward said annular wall for passage through said return space, said bafile plate and said impelling means being fixedly mounted for rotation with said shaft, and means for deflecting at least some of the mixed material from said recirculating space into said return space and then into said mixing space, said inlet being located to channel at least some of the incoming material directly into said return space.

4. In a continuous flow mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having a longitudinal axis, said casing defining a chamber, an inlet leading from a source of unmixed material under pressure through said wall into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft disposed along said axis and mounted for rotation within said chamber, a baffie plate extending transversely of said chamber and dividing said chamber into a mixing space and a recirculating space, mixing elements extending from said first head member toward said baffie plate, cooperating mixing elements extending from said bafile plate toward said first head member, a discharge opening in said baffie plate adjacent said shaft providing communication between said mixing space and said recirculatingspace, said baffie plate terminating short of said wall to define a return space, impelling means spanning a sufiicient distance between said bafile plate and said second head member for impelling at least a substantial amount of the mixed material toward said annular wall for passage through said return space, said baflle plate and said impelling means being fixedly mounted for rotation with said shaft, and means for deflecting at least some of the mixed material from said recirculating space into said return space and then into said mixing space, said deflecting means being disposed in said return space and partially disposed in said recirculating axis, said casing defining a chamber, an inlet leading from a source of material under pressure through said annularwall into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft disposed along said axis and mounted for rotation within said chamber, a battle plate extending transversely of said chamber and dividing said chamber into a mixing space and a recirculating space, mixing elements extending from said first head member toward said bafile plate, cooperating mixing elements extending from said bafile plate toward said first head member, a discharge opening through said bafile plate adjacent said shaft providing communication between said mixing space and said recirculating space, said annular wall having deflecting projections, the space between the periphery of said baffle plate and said annular wall defining a return space, means in said recirculating space for impelling at least a substantial portion of the mixed material toward said annular wall, said deflecting projections being disposed skewed with respect to said longitudinal axis and opening toward said return space to cause the mixed material to be deflected into said return space and then into said mixing space, said bafile plate and said impelling means being fixedly mounted for rotation with said shaft.

6. In a continuous fiow mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having a longitudinal axis, said casing defining a chamber, an inlet leading from a source of material under pressure through said annular wall into said chamber, an outlet in said second head member spaced a substantial distance from said -wall, a shaft disposed along said axis and mounted for rotation within said chamber, a bafiie plate extending transversely of said chamber and dividing said chamber into a mixing space and a recirculating space, mixing elements extending from said first head member toward said bafile plate, cooperating mixing elements extending from said bafile plate toward said first head member, a discharge opening through said baffie plate adjacent said shaft providing communication between said mixing space and said recirculating space, said annular wall having deflecting projections, said bafile plate terminating short of said annular wall to define a return space, impeller blades in said recirculating space for impelling at least a substantial portion of the mixed material toward said annular wall, said baflle plate and said impelling blades being fixedly mounted for rotation with said shaft, each of said impelling blades terminating at an inclined end opening toward said return space to deflect the mixed material into said return space and then into said mixing space. V

7. In a continuous flow mixer: a casing including a first head member and :a second head member joined by an annular wall, an annular recess in at least one of said head members, a compressible O-ring disposed in said recess and in abutment with an annular end of said annular wall, means for holding said O-ring in compression to seal off said chamber, said wall having a longitudinal axis, said casing defining a chamber, an inlet leading from a source of unmixed material under pressure through said wall into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft disposed along said axis and mounted for rotation within said chamber, a baffie plate extending transversely of said chamber and dividing said chamber into a mixing space and a recirculating space, mixing elements extending from said first head member toward said baffle plate, cooperating mixing elements extending from said bafiie plate toward said first head member, a discharge opening in said bafile plate adjacent said shaft providing communication between said mixing space and said recirculating space, said baflle plate terminating short of said wall to define a return space, impelling blades in said recirculating space for impelling at least a substantial portion of the mixed material toward said wall, each impelling blade r 9 having an outward terminal end, the maximum pressure in said chamber being at said terminal ends of said impelling blades and at said return space, said baffie plate and said impelling means being fixedly mounted for rotation with said shaft, and means for deflecting at least some of the mixed material from said recirculating space into said return space and then into said mixing space, said inlet being located to channel at least some of the incoming material directly into the mixed material at the place of maximum pressure.

8. In a continuous fiow mixer: a casing including a,

first head member and a second head member joined by an annular wall, an annular recess in at least one of said head members, a compressible O-rin-g disposed in said recess and in abutment with an annular end of said annular wall, means for holding said 'O-ring in compression to seal olf said chamber, said wall having a longitudinal axis, said casing defining a chamber, an inlet leading from a source of material under pressure through said wall into said chamber, an outlet in saidisec'ond head member spaced a substantial distance from said wall, a shaft disposed along said axis and mounted for rotation within said chamber, a baflie plate extending transversely of said chamber and dividing said chamber into a mixing space and a recirculating space, mixing elements extending from said first head member toward said baffle plate, cooperating mixing elements extending from said baffie plate toward said first head member, -a discharge opening in said baffie plate adjacent said shaft providing communieation between said mixing space and said recirculating space, said baffle plate terminating short of said wall to define a return space, impelling blades in said recirculating space for impelling at least a substantial portion of the mixed material toward said wall, each impelling blade having an outward terminal end, the maximum pressure in said chamber being at said terminal ends of said impelling blades and at said return space, said baffle plate and said impelling means being fixedly mounted for rotation with said shaft, means for deflecting at least some of the mixed material from said recirculating space into said return space and then into said mixing space, said inlet being located .to channel at least some of the incoming material directly into the mixed material at the place of maximum pressure, means for removably mounting said bafile plate and said impelling means as a unit on said shaft, and means for retracting said head member having said recess to provide easy access for demounting said baffie plate and said impelling means.

9. The invention defined in claim 8 wherein said retracting means includes a hinge.

10. The invention defined in claim =8 including removable sealing means for providing a seal between said shaft and said first head member. 7

111. In a continuous fiow' mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having an axis, said casing defining a chamber, spaced apart first and second baffie plates disposed in said chamber and extending transversely relative to said axis, said first baffie plate being adjacent said first head member and said second baffie plate being adjacent said second head member, an inlet leading from a source of material under pressure and opening into a first space between said first head member and said first baffie plate, mixing elements extending from said first head member toward said first baffle plate, cooperating mixing elements extending from said first bafile for impelling material, which has passed through said opening, toward said annular wall, mixing elements extending from said second head member toward said second bafile plate, cooperating mixing elements extending from said second baffie plate toward said second head member, an outlet in said second head member and being spaced a substantial distance from said annular wall, said second space opening into both said first space and a third space between said second bafile plate and said second head member, and a shaft mounting said first and second bafile plates and said impelling means for rotation.

12. In a continuous flow mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having an axis, said casing defining a chamber, spaced apart first and second baffie plates disposed in said chamber and extending transversely relative to said axis, said first bafile plate being adjacent said first head member and said second bafile plate adjacent said second head member, an inlet opening into a first space between said first head member and said first bafile plate, mixing elements extending from said first head member toward said first baffie plate, cooperating mixing elements extending from said first bafile plate toward said first head member, an opening in said first bafile plate through which material can pass from the first space to a second space between said first and second baffie plates, means for deflecting at least some of the impelled material from said second space into said first space, means disposed in said second space for impelling material, which has passed through said opening, toward said annular wall, an outlet disposed axially in said second head member, said second space opening into both said first space and a third space between said second baffle plate and said second head member, and means mounting said first and second baflle plates and said impelling means for rotation, said mounting means terminating short of said outlet in said second head member.

13. In a continuous flow mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having an axis, said casing defining a chamber, an inlet leading from a source of material under pressure into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft disposed along said axis and rotatably mounted within said chamber, a baflle plate disposed in said chamber and extending transversely relative to said axis, with a first space on one side of said bafile plate and a second space on the other side of said baffle plate, mixing elements extending from said first head member toward said baffie plate, cooperating mixing elements extending from said baffie plate toward said first head member, a discharge opening in said baffie plate adjacent said shaft providing communication between said first space and said second space, said baffie plate terminating short of said annular wall, means in said second space for impelling mixed material toward said annular wall, said baffle plate and said impelling means being mounted by said shaft, and means for deflecting at least some of the mixed material from said second space into said first space.

14. In a continuous flow mixer: a casing including a first head member and a second head member joined by a generally annular wall, said wall having an axis, said casing defining a chamber, an inlet leading from a source of material under pressure into said chamber, an outlet in said second head member spaced a substantial distance from said wall, a shaft along said axis and rotat-ably mounted withinsaid chamber, spaced apart first and second bafile plates disposed in said chamber and extending transversely relative to said axis, mixing elements extending from said first head member toward said first baffie plate, cooperating mixing elements extending from said first baflle plate toward said first head member, a discharge opening in said first baffie plate adjacent said shaft providing communication between one side and the other side of said first baflle plate, a space between 11 p 312 said first baffle plate and said annular Wall, means dis- References Cited by the Examiner posed between said first and second bafiie plates for im- UNITED STATES PATENTS pelhng material toward sa1d annular Wall, sa1d baflle 0 plates and impelling means being mounted by said shaft, 2882149 4/1959 Wlnems X and means for deflecting at least some of the mixed ma- 5 2,904,407 9/1959 Rosemhal et terial from between said first and second baffle plates I through said space and to between said first head mem- WALTER L P'lmary Examiner ber and said first baffle plate. .l. M. BELL, Assistant Examiner. 

1. IN A CONTINUOUS FLOW MIXER: A CASING INCLUDING A FIRST HEAD MEMBER AND A SECOND HEAD MEMBER JOINED BY A GENERALLY ANNULAR WALL, SAID WALL HAVING A LONGITUDINAL AXIS, SAID CASING DEFINING A CHAMBER, AN INLET LEADING FROM A SOURCE OF MATERIAL UNDER PRESSURE INTO SAID CHAMBER, AN OUTLET IN SAID SECOND HEAD MEMBER SPACED A SUBSTANTIAL DISTANCE FROM SAID WALL, A SHAFT DISPOSED ALONG SAID AXIS AND MOUNTED FOR ROTATION WITHIN SAID CHAMBER, A BAFFLE PLATE EXTENDING TRANSVERSELY OF SAID CHAMBER AND DIVIDING SAID CHAMBER INTO A MIXING SPACE AND A RECIRCULATING SPACED, MIXING ELEMENTS EXTENDING FROM SAID FIRST HEAD MEMBER TOWARD SAID BAFFLE PLATE, COOPERATING MIXING ELEMENTS EXTENDING FROM SAID BAFFLE PLATE TOWARD SAID FIRST HEAD MEMBER, A DISCHARGE OPENING IN SAID BAFFLE PLATE ADJACENT SAID SHAFT PROVIDING COMMUNICATION BETWEEN SAID MIXING SPACE AND SAID RECIRCULATING SPACE, SAID BAFFLE PLATE TERMINATING SHORT OF SAID WALL TO DEFINE A RETURN SPACE MEANS IN SAID RECIRCULATING SPACE FOR IMPELLING AT LEAST A SUBSTANTIAL PORTION OF THE MIXED MATERIAL TOWARD SAID WALL, SAID BAFFLE PLATE AND SAID IMPELLING MEANS BEING FIXEDLY MOUNTED FOR ROTATION WITH SAID SHAFT, AND MEANS FOR DEFLECTING AT LEAST SOME OF THE MIXED MATERIAL FROM SAID RECIRCULATING SPACE INTO SAID RETURN SPACE AND THEN INTO SAID MIXING SPACE. 